Removing user mode registers

Rework on misa and mstatus

Remove bit_field dependency

asm: set unsafety of `nop` and `delay` functions to safe

... and a small codestyle fix in Cargo.toml file.

Signed-off-by: Zhouqi Jiang <luojia@hust.edu.cn>

Rework of mcause and scause registers

scause: add missing LoadMisaligned

See table 4.2 in privileged spec version 20211203 as found today at
https://riscv.org/technical/specifications/

Skip [] in docs

While working on the peripheral stuff, `cargo doc` kept raising a warning with this macro, as it attempted to find a reference in the crate. This PR fix it

Remove bors

132: Update GitHub workflows r=almindor a=romancardenas

With all the bors thing going on, I've been reading a bit about merge queues etc. and noticed that some of our workflows still use outdated/deprecated actions. This PR fixes this.

Co-authored-by: Román Cárdenas <rcardenas.rod@gmail.com>

129: PLIC peripheral r=romancardenas a=romancardenas

Same as #125 (closing right now) but with a clean commit history. I've been playing around with this implementation and detected nice-to-have features and boring patterns that could be implemented using macros. Pointers to repos that are already working with it:

- [`e310x` PAC](https://github.com/greenlsi/e310x)
- [`e310x-hal` HAL](https://github.com/greenlsi/e310x-hal)
- [`hifive1` BSP](https://github.com/romancardenas/hifive1) with an illustrative [example](https://github.com/romancardenas/hifive1/blob/master/examples/interrupt.rs

)

Co-authored-by: Román Cárdenas <rcardenas.rod@gmail.com>

131: fix a typo r=romancardenas a=OccupyMars2025



Co-authored-by: OccupyMars2025 <31559413+OccupyMars2025@users.noreply.github.com>